Transesterification of castor oil catalyzed by a fermented solid produced by Burkholderia contaminans using a bioreactor coupled with ultrasound irradiation.

In this work, ultrasound was used to assist the ethanolysis of castor oil in a solvent-free system, catalyzed by a dry fermented solid containing the lipase from Burkholderia contaminans (BCFS). Reactions were done at 45°C. The maximum conversion in Erlenmeyer flasks was 71% in 96 h, using a loading of 9% (mass of BCFS in relation to the mass of triacylglycerols in the castor oil) and a molar ratio of ethanol:oil of 6:1, with addition of ethanol in 12 steps. In a packed-bed reactor containing 12 g of BCFS, the conversions were 78% in 48 h, and 83% in 72 h with an ethanol to oil molar ratio of 3:1 and treatment with an ultrasound probe, with maximum power of 500 W, frequency of 20 kHz, and 75% of the maximum power. These results are promising given that, with an ultrasound assisted bioreactor, a higher conversion in a shorter time was achieved, with a lower ethanol to oil molar ratio than was the case in the Erlenmeyer flasks without ultrasound.

Genome sequencing of Burkholderia contaminans LTEB11 reveals a lipolytic arsenal of biotechnological interest.

Burkholderia contaminans LTEB11 is a Gram-negative betaproteobacterium isolated as a contaminant of a culture in mineral medium supplemented with vegetable oil. Here, we report the genome sequence of B. contaminans LTEB11, identifying and analyzing the genes involved in its lipolytic machinery and in the production of other biotechnological products.

The introduction of the fungal D-galacturonate pathway enables the consumption of D-galacturonic acid by Saccharomyces cerevisiae.

BACKGROUND: Pectin-rich wastes, such as citrus pulp and sugar beet pulp, are produced in considerable amounts by the juice and sugar industry and could be used as raw materials for biorefineries. One possible process in such biorefineries is the hydrolysis of these wastes and the subsequent production of ethanol. However, the ethanol-producing organism of choice, Saccharomyces cerevisiae, is not able to catabolize D-galacturonic acid, which represents a considerable amount of the sugars in the hydrolysate, namely, 18 % (w/w) from citrus pulp and 16 % (w/w) sugar beet pulp. RESULTS: In the current work, we describe the construction of a strain of S. cerevisiae in which the five genes of the fungal reductive pathway for D-galacturonic acid catabolism were integrated into the yeast chromosomes: gaaA, gaaC and gaaD from Aspergillus niger and lgd1 from Trichoderma reesei, and the recently described D-galacturonic acid transporter protein, gat1, from Neurospora crassa. This strain metabolized D-galacturonic acid in a medium containing D-fructose as co-substrate. CONCLUSION: This work is the first demonstration of the expression of a functional heterologous pathway for D-galacturonic acid catabolism in Saccharomyces cerevisiae. It is a preliminary step for engineering a yeast strain for the fermentation of pectin-rich substrates to ethanol.

Pectinase activity determination: an early deceleration in the release of reducing sugars throws a spanner in the works!

Recently, it has been suggested that pectinases could be used to hydrolyze pectin in biorefineries based on pectin-rich agro-industrial wastes. However, for this to be viable, the cost of their production would need to be lowered significantly. In fact, over the last few decades, there have been many attempts to improve pectinase production by existing strains or to screen for new strains from environmental isolates. In these studies, it is necessary to measure pectinase activities. Many researchers use single-time-point assays that involve incubation of pectinolytic extracts with pectic substrates for a fixed time, followed by determination of the liberated reducing sugars. However, different researchers use quite different conditions for this assay. Furthermore, no attention has been given to the reaction profile during the assay. In the current work, we show, for the first time, that a significant deceleration of the rate of liberation of reducing sugars occurs over the first ten minutes of the reaction. As a consequence, the incubation time used in a single-time-point assay has a large effect on the value obtained for the activity. In fact, we demonstrate that, depending on the particular combination of incubation time, pectin concentration and reaction temperature, the same extract could be reported to have activities that differ by an order of magnitude. In addition, we show that the relative activities obtained with polygalacturonic acid do not correlate with those obtained with pectin. We conclude that it is currently impossible to make meaningful comparisons between pectinase activities reported in the literature by workers who have used different assay conditions. Therefore there is an urgent need for the development of a standardized assay for evaluating the saccharification potential of pectinase complexes.

Production of rhamnolipids in solid-state cultivation using a mixture of sugarcane bagasse and corn bran supplemented with glycerol and soybean oil.

Rhamnolipid biosurfactants are attracting attention due to their low toxicity, high biodegradability, and good ecological acceptability. However, production in submerged culture is made difficult by severe foaming problems. Solid-state cultivation (SSC) is a promising alternative production method. In the current work, we report the optimization of rhamnolipid production by Pseudomonas aeruginosa UFPEDA 614 on a solid substrate containing sugarcane bagasse and corn bran. The best rhamnolipid production, 45 g/l of impregnating solution used, was obtained with a 50:50 (m/m) mixture of sugarcane bagasse and corn bran supplemented with an impregnating solution containing 6% (v/v) of each of glycerol and soybean oil. This level is comparable with those of previous studies undertaken in solid-state cultivation; the composition of the biosurfactant is similar, but our medium is cheaper. Our work therefore provides a suitable basis for future studies of the development of an SSC-based process for rhamnolipid production.